The present invention relates to a portable actuator assembly for use in the actuation of a control mechanism of a safety switch (which may generally be referred to as the actuation of the safety switch).
Safety switches are well known, and are typically used to prevent access to for example electromechanical machinery when that machinery is in operation. In a conventional arrangement the safety switch is mounted on a doorpost of a machinery guard, and an actuator for the safety switch is mounted on a corresponding door. When the door is closed the actuator engages with the safety switch, which in turn closes a set of electrical contacts which allow power to be supplied to the machinery. This arrangement ensures that power can only be supplied to the machinery when the guard door is shut. When the guard door is opened, the actuator disengages from (i.e. is withdrawn from) the safety switch, thereby opening the electrical contacts and cutting off the supply of power to the machinery.
A typical safety switch comprises a body, in which is provided a set of contacts fixed in position relative to the body. An axially slideable plunger is mounted inside the body, and is moveable relative to the body. The plunger (or another plunger in contact with the plunger, for example a contact block plunger) is provided with another set of contacts. The plunger is biased towards a cam arrangement or other control arrangement by a biasing element, such as a spring. The actuator mentioned above is arranged to engage with the cam arrangement.
In many safety switches, if the actuator is not engaged with the cam arrangement (e.g. if the actuator is not engaged with the safety switch), the cam arrangement is arranged to prevent the contacts on the plunger coming into contact with the contacts in the body of the switch by preventing movement of the plunger (i.e. the plunger is kept in a first plunger position). By preventing the contacts from contacting one another, the switch cannot conduct electricity while the actuator is not engaged with the cam arrangement.
Bringing the actuator into engagement with the cam arrangement causes the cam arrangement to rotate, which in turn causes the plunger (which is biased toward the cam arrangement) to move into a notch provided in the cam arrangement. The plunger is then in a second plunger position. When the plunger moves into the notch, the contacts on the plunger are brought into contact with the contacts of the body of the switch, allowing electricity to flow through the safety switch.
As discussed above, in a conventional arrangement, the safety switch is mounted on a door post of a machinery guard, and an actuator of the safety switch is mounted on a corresponding door of the machinery guard. However, it is also known to alternatively or additionally use one or more further actuators which are not mounted on the door but are instead provided in isolation. Such additional isolated actuators may be used for maintenance, testing, cleaning, or the like. For instance, in one example a manager or supervisor may be responsible for such an isolated actuator. An employee responsible for maintenance may approach the manager or supervisor to request permission to use the isolated actuator. The manager or supervisor may grant such permission, and provide the isolated actuator to the maintenance employee. The maintenance employee may then approach the safety switch, and engage the provided isolated actuator with a safety switch. It is important to note that this isolated actuator is not the actuator mounted to the door. Thus, the door to the machinery guard is not closed when the maintenance employee uses the additional isolated actuator. By using the isolated actuator, the employee may cause electricity to be supplied to machinery within the machinery guard without closing the door, allowing the maintenance employee to test, clean, maintain or the like the machinery when it is in operation, or at least when power is supplied to the machinery.
It is important to try to ensure that the provision of such an isolated actuator, and/or the use of such an isolated actuator, is not abused. For example, it is plausible that the isolated actuator may not be returned to the manager or supervisor, but instead may be used to allow anyone with the isolated actuator to enter the machinery guard while the machinery is operating. This can create a potentially unsafe condition, not only for the user of the isolated actuator, but for any other user or the like working in the vicinity of the machinery or machinery guard. It will be apparent that abuse of the use of such an isolated actuator is undesirable, and should be avoided and/or limited by imposing some sort of control. One way of achieving such control might involve the manager or supervisor requesting the return of the isolated actuator after its use. However, the manager or supervisor may forget to request the return of the actuator, or if a large number of isolated actuators are available, one or more isolated actuators may become easily misplaced. Alternatively or additionally, one or more users may obtain such an isolated actuator without permission of the manager or supervisor, making it difficult or impossible for the manager or supervisor to keep track of the isolated actuators, the location of the isolated actuators and the usage of the isolated actuators.
It is therefore desired to provide an improved or alternative portable actuator assembly which may overcome or substantially mitigate at least one disadvantage of the prior art, whether identified herein or elsewhere, associated with the use of isolated actuators.